In recent years, the transmission of large-volume data such as still image data and moving image data in addition to audio data has become common in cellular mobile communication systems along with increasing use and development of multimedia information. In order to achieve large-volume data transmission, active studies have been carried out on techniques for achieving a high transmission rate using a broad radio band, a MIMO (Multiple-Input Multiple-Output) transmission technique and an interference control technique.
LTE-Advanced (Long Term Evolution Advanced) for which introduction of the aforementioned technique is being studied aims at high speed downlink communication using a maximum of 1 Gbps and requires a communication system that achieves high throughput and is excellent in frequency utilization efficiency. LTE-Advanced promotes implementation of high throughput of a cellular network and improvement of frequency utilization efficiency.
In order to expand a range (coverage area) where high throughput is supported, studies have been carried out on a relay technique that involves placement of a radio communication relay station apparatus (hereinafter, abbreviated as “relay station” or RN (Relay Node)) between a radio communication base station (hereinafter, abbreviated as “base station” or “eNB”) and a radio communication mobile station apparatus (hereinafter, abbreviated as “mobile station” or “UE (User Equipment)”) and that performs communication between the base station and the mobile station via the relay station (e.g., see PTL 1). The use of relay technique allows even a mobile station that cannot directly communicate with a base station to perform communication via a relay station.
In LTE-Advanced, studies have been carried out on a mobile relay technique that involves installation of a relay station on a train, bus or the like. According to the mobile relay technique, since a mobile station connected to a mobile relay which is a relay station moves together with the vehicle, the mobile relay, instead of the mobile station, performs mobile control such as handover with a base station (Donor eNB: DeNB) to which the mobile relay is connected during the ride on the vehicle. Thus, the mobile station need not perform its own mobile control and thereby can reduce signaling traffic associated with the mobile control.
Meanwhile, network sharing has been attracting attention, which allows a network to be shared among a plurality of operators in order to reduce device costs (e.g., see PTL 2). In network sharing, devices such as a base station (eNB) and mobile station (UE) or the frequency band is shared among operators. Network sharing is expected to enable active and efficient use of finite resources such as the frequency band.